1. Field of Invention
The present invention is designed to treat mandible and facial fractures by improving the technique of maxillo-mandibular fixation (MMF) or intermaxillary fixation (IMF).
2. Prior Art
Those skilled in the art of treating fractures of the mandible are familiar with the current techniques in repairing mandible and other facial fractures. Most mandible fracture repairs require immobilization of the jaws in dental occlusion during healing. Achieving stable maxilla-mandibular fixation requires immobilization of the powerful jaw muscles using points of fixation which are strong enough to resist considerable force.
Stable immobilization of the jaws in dental occlusion is achieved by affixing the mandibular to the maxillary teeth (maxillo-mandibular fixation or MMF) Standard maxillo-mandibular fixation is achieved through arch bars wired to multiple teeth with circum-dental wires. Wires are wrapped around the base of each tooth, then those wires are attached to arch bars which approximate the mandibular and maxillary arches. The maxillary and mandibular arch bars subsequently may be wired together. The fixation strength provided by each wire wrapped around each individual tooth is relatively weak, and so substantially all of the teeth are wired so that they collectively provide sufficient strength. However, this wiring technique can be very time-consuming, tedious, and dangerous to surgeons, presenting a real risk of needle sticks and torn gloves. Moreover, it results in a fairly elaborate wiring scheme which can only be released with wire cutters. If a patient vomits, the jaws must be very quickly freed using wire cutters in order to protect the patient's airway. For this reason, the technique poses a real risk of asphyxiation if a patient or care taker is unable to free the jaws in time. There is also a significant risk that a patient will aspirate cut wire either during an emergency release or during the routine installation or removal of the wires.
An alternative technique to arch bar wiring MMF includes the use of screws placed in the cortical bone of the jaw between the tooth-roots as disclosed in U.S. patent application Ser. No. 12/329,263 with holes in the screw-head for wiring. These screws provide adequate fixation strength to resist the jaw muscles because they are driven through dense cortical bone. However, while this technique is faster, there is risk of injury to the toothroots, which would result in tooth death. The level of force required to drive screws into cortical bone, either with a pilot hole or without, is considerable, resulting in a relatively difficult and uncomfortable procedure for the patient. The screws must be placed using instruments such as drills, punches, screw drivers, etc., and many of these instruments are difficult to use within the confines of the mouth, restricting the available angles of approach. The screws can complicate the repair of jaw fractures. Moreover, the technique results in a less stable fixation than arch bar wiring MMF because the points of fixation on the respective jaws are significantly further apart from one another, permitting play in the wires, especially if stretched over time. Additionally, the risk of aspiration with wire-cutter failure remains.
Thus, the traditional methods of immobilizing jaws in dental occlusion for fracture repair have substantial drawbacks. However, those of skill in this art continue to use these methods despite their drawbacks because the conventional wisdom teaches that only the teeth in aggregate and the cortical bone of the jaw permit fixation that is strong enough to resist the jaw muscles. The interdental tissues have always been considered too weak to use for this purpose.